1. Field of the Invention
This invention relates broadly to surgical devices. More particularly, this invention relates to devices for assisting the insertion of a guidewire into a catheter.
2. State of the Art
Catheterization procedures are well known for diagnosis and therapy of lesions in the cardiovascular system. One such procedure is angioplasty, for eliminating or ameliorating the vascular blockage or constriction in blood vessels associated with supplying blood to the heart or other organs. In an angioplasty procedure, an expandable balloon carried by an elongated catheter is introduced into the arterial system of a patient and advanced until it is positioned in the region of the blockage or constriction. Once so positioned, the balloon is expanded by filling it with a fluid. In successful procedures, the expandable balloon presses outwardly against the walls of the artery and expands the artery to a degree to which the artery is either partially or completely reopened to blood flow.
Prior to initiating the angioplasty procedure, a guiding catheter is placed, typically via the femoral artery, into the aorta and its tip is engaged into the coronary arteries which branch from the aorta. Once placed, the guiding catheter acts as a conduit to access the coronary arteries with a guidewire and balloon catheter. The guiding catheter is a portion of plastic tubing having a length of about 95 centimeters, an inside diameter of about 2 millimeters, and an outside diameter of about 2.5 millimeters. A hemovalve, i.e., a valve preventing blood loss through the guiding catheter when a tubular conduit such as a balloon catheter is passed therethrough, is provided at the proximal end of the guiding catheter.
Then, external of the patient, the physician threads a guidewire through a balloon catheter for subsequent insertion through the guiding catheter to the location of the lesion for balloon dilation of the lesion. The guidewire is a metal wire, e.g., titanium or nickel-titanium alloy wire, approximately 175 centimeters in length, and about 0.25 to 0.46 millimeters in diameter. The balloon catheter is an elongate flexible plastic tubular member defining two longitudinal passages and having the balloon located at or adjacent its distal end. One longitudinal passageway defines a conduit through which the guidewire can be passed. The other longitudinal passage defines a conduit in fluid communication with the interior of the balloon and through which inflation fluid can be injected to inflate the balloon. The proximal end of the guidewire is thread into the distal end of the catheter, permitting insertion of the distal end of the guidewire into the patient and subsequent sliding of the distal end of the catheter over the guidewire to position an expandable balloon at the site of the lesion.
While the procedure has been quite effective, the process of threading the guidewire through the balloon catheter remains a frustrating and time consuming task. The guidewire and balloon catheter are both very small in diameter and relatively long, and it is difficult for the physician to hold one in each hand in a manner which facilitates threading the proximal end of the guidewire into the small opening of the distal end of the balloon catheter. In addition, the delicate balloon can be easily and unintentionally damaged by the manipulation required for the threading procedure.
Publication EP 0328760 A2 describes a threader device intended to assist the threading of a guidewire into a catheter. The threader device includes two semi-cylindrical halves each having portions of threads on their exterior surfaces such that when the halves are positioned together to form a cylinder, the exterior surfaces of the two halves together define complete external helical threads. A removable threaded collar is positioned over the external threads and holds the halves together. The two halves together define a passage having a cylindrical central portion and two funnel-shaped end portions. The funnel at a first end portion is sized to readily receive an end of the catheter, while the funnel at the second end portion has a larger end adapted to readily receive the guidewire and a tapered end sized smaller than the outer diameter of the catheter yet sufficiently large to receive an end of the guidewire.
In use, the catheter is pushed into the funnel at the first end portion, through the central portion, and butt against the funnel at the second end portion. The guidewire is then inserted through the funnel of the second end portion where it is directed into the catheter, and a sufficient length of guidewire is fed therein.
However, the device of publication EP 0328760 A2 has several significant drawbacks. First, after the guidewire is threaded into the catheter, the threader device must be removed from over the catheter to permit the distal end of the catheter to enter the guiding catheter and the human body. However, it is difficult to remove the threader device from over the catheter and the guidewire after the guidewire has been threaded into the catheter. While the collar can be removed from over the halves to free the halves from the catheter and guidewire, the collar is still trapped over the catheter and guidewire. The only way to remove the collar is to slide the collar over the relatively long length of either the catheter or the guidewire. This requires complete uncoiling of one of the otherwise neatly coiled catheter and guidewire. Otherwise, the collar must be obtrusively left thereover. Second, the unassembled device includes three separate and distinct elements, two halves and a collar, any of which may become misplaced or lost. Third, the passageway of the threader device is not particularly adapted to receive the balloon at the distal end of a balloon catheter, as the cylindrical passage in the device is configured only for use with non-balloon catheters. Fourth, even if a balloon is forced into the passageway, the passageway is apparently not of sufficient length to surround a balloon over the entire length of the balloon. As such, a portion of the balloon may extend external of the threader device and potentially be subject to inadvertent damage.